JP2009045904A - Injection molding machine having screw rotational torque monitoring function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding machine capable of monitoring a screw rotational torque by setting an allowable ceiling value of the rotational torque during metering in terms of screw rotational speed, transfer distance and time passage. <P>SOLUTION: This injection molding machine includes (1) an instrumentation means which measures screw rotational speed and screw rotational torque per specified time during metering, (2) a storage means which stores the screw rotational speed and the screw rotational torque, (3) a means to seek a maximum screw rotational torque at a screw rotational speed by entering the screw rotational speed and the screw rotational torque stored in the storage means as a presupposed function, (4) a means to set an allowable ceiling value of the screw rotational torque at each screw rotational speed based on the sought maximum screw rotational torque, and (5) a means to alter or stop a screw rotational operation, when the screw rotational torque above the allowable ceiling value, is detected during the following metering. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an injection molding machine, and more particularly, to a numerical controller that prevents screw abnormality by monitoring and controlling screw rotational torque.

The injection molding machine is equipped with a function to protect the screw by immediately limiting or stopping the screw operation when excessive screw rotation torque exceeding the preset upper limit value of screw rotation torque is detected. There is.
In setting the allowable upper limit value of the screw rotational torque, a method of obtaining from the material mechanical strength calculation based on the tensile strength and torsional fatigue strength of the screw material in advance, or experimentally under a condition in which the screw rotational torque is sufficiently limited. There is a method of measuring and obtaining from actual measurement values.

  However, there are cases in which the screw breaks with a screw rotation torque that is less than or equal to the allowable upper limit value of the screw rotation torque, and there is a need for an injection molding machine that can set the allowable upper limit value of the screw rotation torque more appropriately. Also, the torque that breaks the screw is much larger than the torque used in normal molding, so if you do not limit the screw rotation with a torque value closer to actual molding, the screw rotation torque will be abnormal for some reason When it rises, there is a problem that a high load is applied to the screw until the allowable upper limit value is reached.

  As described in Patent Document 1, a method for preventing breakage of a screw by setting an allowable upper limit value of screw rotational torque is known. As a method of setting the allowable upper limit value of the screw rotational torque, there is a method of obtaining it from material mechanical strength calculation. However, in order to perform calculations with high accuracy, a lot of data on the strength of the screw material, such as tensile strength and torsional fatigue strength, is required. More than the number of tests. There are a wide variety of screw shapes, and it is difficult to determine the strength of the screw correctly only by calculating the material mechanical strength.

  Alternatively, perform a test weighing operation to obtain the reference screw rotation torque required for the measurement operation from the actual measurement value, and set the allowable upper limit value of the screw rotation torque in consideration of the allowable upper limit value so as not to hinder the molding. There is a way. However, in this method, since the measurement conditions vary depending on the resin and the molded product, it takes time if it is not automated.

  Further, as described in Patent Document 2, a discrimination target section and a permissible range are set according to the screw movement distance and the elapsed time after the start of measurement, and the drive torque of the screw rotation motor in the discrimination target section is detected and allowed. The function of detecting an abnormality in measurement by comparing with a range is known, but an operator must determine the allowable range of the driving torque of the screw rotation motor and manually input it. Since the allowable range varies greatly depending on the mold and resin, the determination is not easy. Even in the automatic setting, monitoring of the driving torque of the screw rotation motor is only used for determining whether the molded product is good or bad, and it is not used for countermeasures against screw breakage prevention.

  As described in Patent Document 3, the limit torque value of the electric servo motor at the time of the test shot is set to a value with a sufficient margin, and the actual torque of the electric servo motor at the time of the test shot is measured, A function of setting a limit torque value of an electric servo motor during continuous molding operation based on actually measured torque data when satisfactory resin kneading and plasticization is achieved in a test shot is known. Here, the measured torque at the screw movement distance in all weighing processes is graphically displayed, but it is not necessary to graphicize all the measured torque for the measurement to set the limit torque value, so select only the necessary data. The burden on the storage capacity is smaller when measuring and storing.

JP-A-7-32430 JP-A-6-297532 JP-A-9-174737

  It is an object of the present invention to set an allowable upper limit value of screw rotation torque by measuring and storing the screw rotation torque being measured during continuous molding, and to perform complicated material mechanical for setting the upper limit value of screw rotation. An object of the present invention is to provide an injection molding machine that does not require strength calculation and tests for actually measuring screw rotational torque.

  It is another object of the present invention to provide an injection molding machine capable of monitoring torque by setting an optimum allowable upper limit value of screw rotation torque for each state during metering according to screw rotation speed, screw movement distance, and elapsed time.

  The invention according to claim 1 of the present application is directed to measuring means for measuring screw rotation speed and screw rotation torque at predetermined time intervals or for predetermined screw movement distances during measurement, and the screw rotation speed obtained by the measurement means. Storage means for storing the screw rotation torque, means for obtaining the maximum screw rotation torque at the screw rotation speed by inputting the screw rotation speed and screw rotation torque stored in the storage means into a function assumed in advance; A means for setting an allowable upper limit value of the screw rotation torque at each screw rotation speed based on the maximum screw rotation torque, and changing or stopping the screw rotation operation when a screw rotation torque exceeding the allowable upper limit value is detected during the subsequent measurement. An injection molding machine comprising means for performing

  According to a second aspect of the present invention, there is provided measuring means for measuring screw rotation speed and screw rotation torque at predetermined time intervals or predetermined screw movement distances during measurement, and the screw rotation speed and screw obtained by the measurement means. Storage means for storing the rotational torque; means for obtaining the maximum screw rotational torque at the screw rotational speed by inputting the screw rotational speed and screw rotational torque stored in the storage means into a function assumed in advance; An injection molding machine comprising: means for setting an allowable upper limit value of screw rotation torque at each screw rotation speed based on screw rotation torque; and means for limiting drive torque applied to the screw to the allowable upper limit value. is there.

  According to a third aspect of the present invention, there is provided measuring means for measuring screw rotation speed and screw rotation torque at predetermined time intervals or at predetermined screw movement distances during measurement, and the screw rotation speed and screw rotation torque by the measurement means. Is measured for a predetermined number of moldings, the screw rotation speed obtained by the measurement and the screw rotation torque are stored, and the screw rotation speed and screw rotation torque stored in the storage means are assumed in advance. Entering into the function, a means for obtaining an approximate expression representing the relationship between the screw rotation speed and the maximum screw rotation torque at the screw rotation speed, and by giving the screw rotation speed to the obtained approximate expression, an allowable upper limit value of the screw rotation torque Means to set and allow screw rotation above the allowable upper limit during subsequent weighing Upon detecting a torque, an injection molding machine, characterized in that it comprises means to change or stop the screw rotating operation.

  According to a fourth aspect of the present invention, there is provided measuring means for measuring screw rotation speed and screw rotation torque at predetermined time intervals or at predetermined screw movement distances during measurement, and the screw rotation speed and screw rotation torque by the measurement means. Is measured for a predetermined number of moldings, and the screw rotation speed and screw rotation torque obtained by the measurement are stored, and the screw rotation speed and screw rotation torque stored in the storage means are assumed in advance. Entering into the function, a means for obtaining an approximate expression representing the relationship between the screw rotation speed and the maximum screw rotation torque at the screw rotation speed, and by giving the screw rotation speed to the obtained approximate expression, an allowable upper limit value of the screw rotation torque is obtained. The setting means and the driving torque applied to the screw are set to this allowable upper limit. An injection molding machine, characterized by comprising means for limited.

According to a fifth aspect of the present invention, the screw rotation torque is measured based on the screw rotation speed and the screw rotation torque measured every predetermined time or every predetermined distance during measurement after the allowable upper limit value of the screw rotation torque is set. The injection molding machine according to any one of claims 1 to 4, further comprising means for updating the upper limit value.
The invention according to claim 6 is characterized in that the upper limit value of the screw rotation torque is set for each of the case where the screw rotates forward and the case where the screw rotates backward. It is a molding machine.
The invention according to claim 7 is the injection molding machine according to any one of claims 1 to 4, further comprising means for storing the set allowable upper limit value of the screw torque in association with mold information.
The invention according to an eighth aspect is the injection molding machine according to any one of the first to fourth aspects, wherein a plurality of functions are prepared as the function assumed in advance, and a means for selecting any one of the functions is provided.
The invention according to claim 9 is characterized in that the allowable upper limit value of the screw rotational torque is set by adding a constant torque to the maximum value of the screw rotational torque or multiplying by a constant coefficient. An injection molding machine according to claim 4.

  The invention of the present application can measure and store the screw rotation torque being measured during continuous molding, and set an allowable upper limit value of the screw rotation torque, so that complicated material mechanical strength calculation, screw rotation torque is actually measured Does not require testing for.

In addition, during the continuous molding, the allowable upper limit value of the screw rotational torque can be updated every time a preset number of moldings is reached. Since the allowable upper limit value of the screw rotation torque set in the actual molding is lower than the torque that can break the screw, the screw rotation can be restricted before a large load is applied to the screw.
Since only data necessary for setting the allowable upper limit value of the screw rotational torque is selected and measured and stored, the burden on the storage capacity is small.

A first embodiment of the present invention will be described below with reference to the drawings.
Prior to setting the allowable upper limit value of the screw rotational torque of the present invention, a common upper limit value of the fixed screw rotational torque is set in all the moldings separately from the allowable upper limit value of the screw rotational torque according to the present invention. This common permissible upper limit value is set to a torque value with a sufficient margin. Under the condition that the screw operation is limited by the common upper limit value of the fixed screw rotational torque, the upper limit value of the screw rotational torque according to the present invention is set.

Next, measurement for setting an allowable upper limit value of the initial screw rotational torque is started. Here, the “allowable upper limit value of the initial screw rotational torque” means that the measurement of the screw rotational torque T _{n at} the screw rotational speed R _n is started immediately after the actual molding is started, and the preset number of molding data The allowable upper limit value of the screw rotation torque set from

  In order to strictly set the allowable upper limit value of the screw rotational torque, data of a larger number of moldings is required. Initially, the allowable upper limit value of the initial screw rotational torque is set from data of a smaller number of moldings. Since the allowable upper limit value of the initial screw rotational torque obtained from the actual molding torque value is lower than the allowable upper limit value of the common fixed screw rotational torque, there is a limit before applying high rotational torque to the screw. Can be added.

  Here, an example of setting the allowable upper limit value of the initial screw rotational torque is shown. In this example, the allowable upper limit value of the initial screw rotational torque is set from the measurement data for the number of moldings 5 times from the start of molding.

  First, screw rotation speed R (a, n) and screw rotation torque T (a, n) are measured at every preset elapsed time from the start of measurement of the molding number a to the end of measurement, and data DA {R ( a, n), T (a, n)} are stored in the table TA (Table 1). This measurement and storage is executed from the first molding.

When the number of forming reaches 5 times, from the measured data group table TA (Table 1), the maximum value T _{k max} of the screw rotation torque in the range R _{k-1 to} R _k of the screw rotation speed set in advance and the value at that time The screw rotation speed R _{k max} is extracted and stored in the table TB (Table 2) as data DB (R _{k max} , T _{k max} ). Initial screw rotation torque in the range of screw rotation speeds R _{k-1 to} R _k by adding a safety allowance A to the maximum screw rotation torque value T _{k max} stored in table TB (Table 2) An allowable upper limit value T _{k max} + A is set.

  As described above, even if the number of data is small, the allowable upper limit value of the initial screw rotation torque obtained from the actual molding torque value is lower than the allowable upper limit value of the common fixed screw rotation torque. This value is sufficiently effective for prevention.

Here, in order to set the allowable upper limit value of the screw rotational torque more strictly, the following measurement is performed. The number of moldings set in advance as the number of data to be aggregated is increased, and the screw rotation torque T _n at the screw rotation speed R _n is measured in the same manner as the setting of the allowable upper limit value of the initial screw rotation torque of the above five molding numbers.

  First, the number of moldings set in advance as the number of data to be tabulated is increased, and the table TA (Table 1) is reset. The screw rotation speed R (a, n) and screw rotation torque T (a, n) are measured at predetermined elapsed times from the start of measurement to the end of measurement, and data DA {R (a, n), T ( a, n)} is stored in the table TA (Table 1). This is continued up to a preset number of moldings.

When the preset number of moldings is reached, the maximum value T _{k max} of the screw rotation torque in each screw rotation speed range R _{k-1 to} R _k is extracted from the measured data table TA (Table 1). Stored as DC (R _{k max} , T _{k max} ) in the table TC (Table 3).

Data DB (R _{k max} , T _{k max} ) of table TB (Table 2) and data DC (R _{k max} , T _{k max} ) of table TC (Table 3) in each screw rotation speed range R _{k-1 to} R _k ) And the smaller data is stored in the table TD (Table 4) as data DD (R _{k max} , T _{k max} ).

The screw rotation torque in the screw rotation speed range R _{k-1 to} R _k is _obtained by adding a margin value A for safety to the maximum screw rotation torque value T _{k max} stored in the table TD (Table 4). An allowable upper limit value T _{k max} + A is set.

In actual molding operation, when detecting a screw rotating torque exceeding this allowable upper limit set the allowable upper limit T _{k max} + A for the screw rotating torque in the range R _k-1 ~R _k screw speed Changes or stops the screw rotation operation so that the screw rotation torque is less than or equal to the allowable upper limit value.

  Next, the data in the table TA (Table 1), the table TB (Table 2), and the table TC (Table 3) are deleted. Then, the data in the table TD (Table 4) is stored again in the table TB (Table 2), and the data in the table TD (Table 4) is deleted after the storage.

The number of moldings for setting the allowable limit value of the screw rotational torque is reset, and measurement is started again. Measurement and storage in the table TA (Table 1) are continued until a preset number of moldings is reached. When the preset number of moldings is reached, the maximum value T _{k max} of the screw rotation torque in each screw rotation speed range R _{k-1 to} R _k is extracted, and DC (R _{k max} , T _{k max} ) is stored in the table TC. Store as.
Thereafter, as long as the injection molding is continued, the allowable upper limit value of the screw rotational torque is repeatedly measured, and the allowable upper limit value of the screw rotational torque is updated.

As the allowable upper limit value of the screw rotation torque, BT _{k max} may be _obtained by multiplying the safety factor B instead of adding the margin value A for which safety is expected. Further, when it is desired to set a high allowable upper limit value of the screw rotation torque, the data DD (R _{k max} , T _{k max} ) stored in the table TD (Table 4) is the data DB (R _k ) of the table TB (Table 2). _max , T _{k max} ) and the data DC (R _{k max} , T _{k max} ) in the table TC (Table 3) may be compared so that the larger screw rotation torque value can be selected. Regardless of whether the larger one is selected or the smaller one, the margin value A or the safety factor B can be set as an allowable upper limit value of the screw rotation torque that does not cause a problem in the actual injection molding operation.

  FIG. 1 is a flowchart of a processing algorithm for setting an allowable upper limit value of the screw rotation torque according to the first embodiment of the present invention. Hereinafter, this flowchart will be described in accordance with each step.

Step A1: A fixed screw rotation torque allowable upper limit value is set.
Step A2: The table TA (Table 1) that stores the screw rotation speed and the screw rotation torque is reset for each elapsed time from the start of measurement to the end of measurement.
Step A3: Data DA {R by measuring screw rotation speed R (a, n) and screw rotation torque T (a, n) for each preset elapsed time from the start of measurement of the molding number a to the end of measurement. (a, n), T (a, n)} is stored in the table TA (Table 1).
Step A4: The measurement is finished with a preset number of moldings.
Step A5: The maximum screw rotation torque T _{k max} and the screw rotation speed R _{k max} at that time in each screw rotation speed range R _{k-1 to} R _k are extracted from the table TA (Table 1), and the data DB (R _{k max} , T _{k max} ) is stored in the table TB (Table 2).
Step A6: A margin value A for safety is added to the maximum screw rotation torque T _{k max} in each screw rotation speed range R _{k−1 to} R _k to set it as the initial screw rotation torque allowable upper limit value.

Step A7: Reset the data in the table TA (Table 1).
Step A8: Screw rotational speed R (a, n) and screw rotational torque T (a, n) are measured at predetermined elapsed time from the start of measurement to the end of measurement for the number of moldings a, and data DA {R (a, n), T (a, n)} is stored in the table TA (Table 1).
Step A9: Continue measurement up to a preset number of moldings.
Step A10: End measurement.
Step A11: The maximum value T _{k max} of the screw rotation torque in each screw rotation speed range R _{k-1 to} R _k is extracted from the table TA (Table 1), and DC (R _{k max} ) is stored in the table TC (Table 3). , T _{k max} ).
Step A12: Data DB (R _{k max} , T _{k max} ) of table TB (Table 2) and data DC (R _{k max} , Table TC) of table TB (Table 2) in each screw rotation speed range R _{k-1 to} R _k T _{k max} ) and the smaller data is stored as data DD (R _{k max} , T _{k max} ) in the table TD (Table 4).

Step A13: The screw rotation torque is calculated by adding a margin value A for safety to the maximum screw rotation torque T _{k max} in each screw rotation speed range R _{k-1 to} R _k stored in the table TD (Table 4). Set as the allowable upper limit.
Step A14: The data in the table TA (Table 1), table TB (Table 2), and table TC (Table 3) is reset.
Step A15: The data in the table TD (Table 4) is moved to the table TB (Table 2), and the data in the table TD is reset.
Step A16: It is determined whether or not molding is completed. If molding is not completed, the process returns to Step A8. If molding is completed, the process ends.

FIG. 2 is a graph showing the relationship between the screw rotation speed and the screw rotation torque and the allowable upper limit value of the screw rotation torque in the first embodiment of the present invention. The horizontal axis of the graph represents the screw rotation speed, and the vertical axis represents the magnitude of the screw rotation torque. FIG. 2 shows the screw rotation speed R (a, n) and screw rotation torque T (a, n) for each number of moldings recorded in the table TA (Table 1) in the screw rotation speed range R ₁ to R ₁ . R _2, ... R _{k-1 to} R _k .

Next, a second embodiment of the present invention will be described with reference to the drawings.
Prior to setting the allowable upper limit value of the screw rotational torque of the present invention, a common upper limit value of the fixed screw rotational torque is set in all the moldings separately from the allowable upper limit value of the screw rotational torque according to the present invention. This common allowable upper limit value is set to a torque value with a sufficient margin. Under the condition that the screw operation is limited by the common upper limit value of the fixed screw rotational torque, the upper limit value of the screw rotational torque according to the present invention is set.

First, measurement for setting the allowable upper limit value of the initial screw rotational torque is started. The “allowable upper limit value of the initial screw rotational torque” means that the measurement of the screw rotational torque T _{n at} the screw rotational speed R _n is started immediately after the actual molding is started, and the preset number of molding data is used. This is the allowable upper limit value of the set screw rotation torque.

  In order to set a strict allowable upper limit value of the screw rotational torque, data of a larger number of moldings is necessary. Initially, an allowable upper limit value of the initial screw rotational torque is set from data of a smaller number of moldings. Since the allowable upper limit value of the initial screw rotational torque obtained from the actual molding torque value is lower than the allowable upper limit value of the common fixed screw rotational torque, a limit is imposed before high torque is applied to the screw. be able to.

  Here, an example of setting the allowable upper limit value of the initial screw rotational torque will be shown. In this example, the allowable upper limit value of the initial screw rotational torque is set from data for the number of moldings five times from the start of molding. The screw rotation speed R (a, n) and the screw rotation torque T (a, n) are set as data DA {R (a, n), for each preset elapsed time from the start of measurement to the end of measurement for the molding number a. T (a, n)} is stored in the table TA (Table 1). This measurement and storage is executed from the first molding.

When the number of forming reaches 5 times, from the measured data group table TA (Table 5), the maximum value T _{k max} of the screw rotation torque in the preset screw rotation speed range R _{k-1 to} R _k and the current time The screw rotation speed R _{k max} is extracted and stored in the table TB (Table 6) as data DB (R _{k max} , T _{k max} ).

From this data, an approximate expression F (R) representing the relationship between the screw rotation speed R _{k max} and the maximum screw rotation torque T _{k max} is _obtained . In many types of resin injection molding, the screw rotational torque tends to increase as the screw rotational speed increases, so it is appropriate to fit the approximate expression F (R) to a monotonically increasing function. Examples of the function include a linear expression (Expression 1), a quadratic expression (Expression 2) to an n-order polynomial (Expression 3), and an irrational function (Expression 4). In some resins, the screw rotation torque does not tend to increase as the screw rotation speed increases. In this case, the nth order polynomial (Equation 3) is applied to the approximate expression F (R). To do. Which function is to be selected is to determine the optimum order n from the actual molding on a trial basis, taking into account the calculation processing capability of the injection molding machine.

ここでは、Ｒの無理関数の式（数式４）に近似する。まず、ｑ＝１／２、データ数をm個として、最小二乗法を用いて数式４の係数ａ及びｂの値を求める。近似式を数式５

Here, it approximates to the expression of the irrational function of R (Formula 4). First, assuming that q = 1/2 and the number of data is m, the values of the coefficients a and b in Equation 4 are obtained using the least square method. Approximation formula is expressed as Formula 5

と考える。このときの残差二乗和は、

I think. The residual sum of squares at this time is

である。

It is.

Next, the values of a and b that minimize _Se are obtained. Considers S _e as a function of (a, b), a, summarized to expand at a 0 and partial differential in b, the following simultaneous equations are obtained.

これを解くとa、bは下記の通りになる。

Solving this, a and b are as follows.

However, F (R) = a√R + b (Formula 5) is an approximate expression, and not all measured screw rotational torque values T are T <F (R) <a√R + b.
Therefore, the ratio ρ between the maximum value T _{k max} of the screw rotation torque stored in the table TB (Table 6) and the screw rotation torque value according to the approximate expression is _obtained . This maximum value ρ _max is multiplied by F (R). _{That, F (R) = ρ max} a√R is an envelope curve including the maximum values of the data group in the table TA (TABLE 5). Further, the margin value A for safety is added to set the allowable upper limit value T _max of the initial screw rotational torque.

  As described above, even if the number of data is small, the allowable upper limit value of the initial screw rotational torque obtained from the actual screw rotational torque value of the molding is lower than the allowable upper limit value of the common fixed screw rotational torque. It is a value that is sufficiently effective for preventing breakage.

  Further, in order to set a strict allowable upper limit value of the screw torque, the following measurement is performed. The number of moldings set in advance as the number of data to be aggregated is increased, and the screw rotation speed Tn at the screw rotation speed Rn is measured in the same manner as the setting of the allowable upper limit value of the initial screw rotation torque of the above-described five molding numbers.

First, the number of moldings set in advance as the number of data to be tabulated is increased, and the table TA (Table 5) is reset. The screw rotation speed R (a, n) and screw rotation torque T (a, n) are measured at predetermined elapsed times from the start of measurement to the end of measurement, and data DA {R (a, n), T ( a, n)} is stored in the table TA (Table 5). This is continued up to a preset number of moldings. When the number of moldings set in advance is reached, the maximum value T _{k max} of the screw rotation torque in each screw rotation speed range R _{k-1 to} R _k is extracted from the measured data group table TA (Table 5). Stored in TC (Table 7) as DC (R _{k max} , T _{k max} ).

Data DB (R _{k max} , T _{k max} ) of table TB (Table 6) and data DC (R _{k max} , T _{k max} ) of table TC (Table 7) in each screw rotation speed range R _{k-1 to} R _k ) And the smaller data is stored in table TD (Table 8) as data DD (R _{k max} , T _{k max} ).
Obtaining the table TD screw rotation speed from the data (Table 8) R _{k max} and maximum screw rotating torques T _{k max} approximate expression F representing the relationship between (R). The method for obtaining the approximate expression is as described above.
The ratio ρ between the data DD (R _{k max} , T _{k max} ) stored in the table TD (Table 8) and the approximate expression is obtained. This maximum value ρ _max is obtained and multiplied by F (R). Further, a margin value A for safety is added and set as an allowable upper limit value T _max of the screw rotation torque (see FIG. 6).

By substituting the screw rotation speed at each moment of measurement into Formula 10 which is an approximate expression that gives the allowable upper limit value T _max of the screw rotation torque, the allowable upper limit value of the screw rotation torque at each moment is obtained. When a screw rotation torque exceeding 1 is detected, the screw rotation operation is changed or stopped so that the screw rotation torque is less than or equal to the allowable upper limit value. Alternatively, when the allowable upper limit value of the screw rotation torque at the set value is obtained by substituting the set screw rotation speed for measurement into the approximate expression 10, and when the screw rotation torque exceeding this allowable upper limit value is detected. Changes or stops the screw rotation operation so that the screw rotation torque is less than or equal to the allowable upper limit value.

Next, the data in the table TA (Table 5), the table TB (Table 6), and the table TC (Table 7) are deleted. The data in the table TD (Table 8) is stored again in the table TB (Table 6), and the data in the table TD is also deleted after the storage. The molding number for setting is reset and measurement is started again. Measurement and storage in the table TA (Table 5) are continued until the preset number of moldings is reached. When the number of moldings set in advance is reached, the maximum value T _{k max} of the screw rotation torque in each screw rotation speed range R _{k-1 to} R _k is extracted, and DC (R _{k max} , Store as T _{k max} ). From this point on, as long as the molding is continued, the allowable upper limit value of the screw rotational torque is updated repeatedly. Instead of adding the margin value A in anticipation of safety, a safety factor B may be multiplied to obtain T = Bρ _max (a√R + b).

When it is desired to set the allowable upper limit value of the screw rotation torque high, the data DD (R _{k max} , T _{k max} ) stored in the table TD (Table 8) is the data DB (R _{k max} , T _{k max} ) and data DC (R _{k max} , T _{k max} ) in table TC (Table 7) may be compared so that the larger torque value can be selected.

FIG. 3 is a graph showing that the approximate expression representing the relationship between the screw rotational speed R _{k max} and the maximum screw rotational torque T _{k max} is a monotonically increasing linear function.
FIG. 4 is a graph showing that an approximate expression representing the relationship between the screw rotation speed R _{k max} and the maximum screw rotation torque T _{k max} is an n-order function (n> 1) such as a quadratic function.
FIG. 5 is a graph showing that the approximate expression representing the relationship between the screw rotation speed R _{k max} and the maximum screw rotation torque T _{k max} is an irrational function such as a √ function.
FIG. 6 is a graph showing the relationship between the screw rotation speed and the screw rotation torque and the allowable upper limit value of the screw rotation torque set by the approximate expression in the second embodiment of the present invention.
FIG. 7 is a flowchart of a processing algorithm for setting the allowable upper limit value of the screw rotational torque according to the second embodiment of the present invention.

Hereinafter, this flowchart will be described in accordance with each step.
Step B1: A fixed screw rotation torque allowable upper limit value is set.
Step B2: The table TA (Table 5) that stores the screw rotation speed and the screw rotation torque is reset for each elapsed time from the start of measurement to the end of measurement.
Step B3: Data DA {R by measuring screw rotation speed R (a, n) and screw rotation torque T (a, n) for each preset elapsed time from the start of measurement of the molding number a to the end of measurement. It is stored in the table TA (Table 5) as (a, n), T (a, n)}.
Step B4: The measurement is finished with a preset number of moldings.
Step B5: The maximum screw rotation torque T _{k max} and the screw rotation speed R _{k max} at that time in each screw rotation speed range R _{k-1 to} R _k are extracted from the table TA (Table 5), and the data DB (R _{k max} , T _{k max} ) in the table TB (Table 6).
Step B6: An approximate expression F (R) is created from the data in the table TB (Table 6).
Step B7: Multiply the maximum ratio ρ _max between the measured torque value and the approximate torque value by F (R), and add a margin value A that allows for safety to F (R) to set as an initial upper limit value of the screw rotation torque. .
Step B8: Reset the data in the table TA (Table 5).
Step B9: Screw rotational speed R (a, n) and screw rotational torque T (a, n) are measured at predetermined elapsed time from the start of measurement to the end of measurement for the molding number a, and data DA {R It is stored in the table TA (Table 5) as (a, n), T (a, n)}.
Step B10: Continue measurement up to a preset number of moldings.
Step B11: The measurement is finished.

Step B12: The maximum value T _{k max} of the screw rotation torque in each screw rotation speed range R _{k-1 to} R _k is extracted from the table TA (Table 5), and DC (R _{k max} is stored in the table TC (Table 7). , T _{k max} ).
Step B13: Data DB (R _{k max} , T _{k max} ) of table TB (Table 6) and data DC (R _{k max} , Table TC) of table TB (Table 6) in each screw rotation speed range R _{k-1 to} R _k T _{k max} ) and the smaller data is stored in the table TD (Table 8) as data DD (R _{k max} , T _{k max} ).

Step B14: Create an approximate expression F (R) from the data of the table TD (Table 8).
Step B15: Multiply F (R) by the maximum ratio ρ _max between the actually measured torque value and the approximate torque value, and add a margin value A that allows for safety to F (R) to set as an allowable upper limit value of the initial screw rotational torque. .
Step B16: The data in the table TA (Table 5), table TB (Table 6), and table TC (Table 7) is reset.
Step B17: The data of the table TD (Table 8) is moved to the table TB (Table 6), and the data of the table TD (Table 8) is reset.
Step B18: It is determined whether or not the molding is finished. If the molding is not finished, the process returns to Step B9. If molding is completed, the process ends.

Next, a third embodiment of the present invention will be described with reference to the drawings.
In addition to the allowable upper limit value of the screw rotational torque according to the present invention, the allowable upper limit value of the fixed screw rotational torque common to all moldings is set. This is set to a value with a sufficient margin. Under the condition that the screw operation is restricted by the common upper limit value of the fixed screw rotational torque, the upper limit value of the screw rotational torque according to the present invention is set.

First, measurement for setting an allowable upper limit value of the initial screw rotational torque is started. The allowable upper limit value of the initial screw rotation torque is set from data of a small number of preset moldings, starting measurement of the screw rotation speed R _n and screw rotation torque T _n immediately after the actual molding starts. This is the allowable upper limit value of the screw rotation torque. To set an exact upper limit value for screw rotation torque, more data on the number of moldings is required. However, the upper limit value for the initial screw rotation torque obtained from the actual molding torque value is fixed to a common fixed value. Since it becomes a value lower than the allowable upper limit value of the screw rotation torque, it is possible to apply a restriction before applying high torque to the screw.

The example of the setting of the allowable upper limit of initial screw rotational torque is shown. In this case, the allowable upper limit value of the initial screw rotational torque is set from the data for the number of moldings five times from the start of molding.
The screw rotation speed R (a, n) and the screw rotation torque T (a, n) are measured at predetermined time intervals from the start of measurement of the molding number a to the end of measurement, and data DA {R (a, n), T (a, n)} are stored in the table TA (Table 9).

  When the number of moldings reaches 5, the approximate expression F (R) representing the relationship between the screw rotation speed R (a, n) and the screw rotation torque T (a, n) from the data group stored in the table TA (Table 9). Ask for. In many types of resin molding, the screw rotation torque tends to increase as the screw rotation speed increases, and when the screw rotation speed is 0, it is obvious that the screw rotation torque is 0. It is appropriate to apply the approximate expression F (R) to a monotonically increasing function passing through the origin.

  The function includes an exponential function (formula 11) including a linear function and a quadratic function. Further, in some types of resins, those in which the screw rotation torque does not tend to increase as the screw rotation speed increases correspond to the case where the nth order polynomial is applied to the approximate expression F (R). Which function is to be selected is to determine the optimum order n from the actual molding on a trial basis, taking into account the calculation processing capability of the injection molding machine.

In the third embodiment, it approximates an irrational function. First, the value of a ₁ in Equation 12 is obtained using the least square method. Consider the approximate expression as Equation 12,

データ数をm個として、この時の残差二乗和は数式１３

The number of data is m, and the residual sum of squares at this time is expressed by Equation 13

である。ここで、S_eを最小にするa₁の値を求める。しかし、数式１２は近似式であることから、実測スクリュー回転トルク値ＴすべてがＴ＜Ｆ₁（Ｒ）＝ａ₁√Ｒとは限らない。そこで、ＴＡに格納されているデータすべてのスクリュー回転速度R(a , n)を数式１２に代入して、近似式によるトルク値F{R(a , n)}を求め、実測スクリュー回転トルク値Tとの比率ρ₁を求める。この最大値ρ_1maxを求めて、F(R)に乗じる。つまり、Ｆ（Ｒ）＝ρ_1maxａ₁√ＲはテーブルＴＡ（表９）のデータ群の最大値を包括する包絡線となる。さらに安全を見込んだ余裕値Aを加算して初期スクリュー回転トルクの許容上限値T_{1 max}として設定する。

It is. Here, finding the value of a ₁ that minimizes S _e. However, since Expression 12 is an approximate expression, not all measured screw rotational torque values T are always T <F ₁ (R) = a ₁ √R. Therefore, all the screw rotation speeds R (a, n) stored in TA are substituted into Equation 12 to obtain a torque value F {R (a, n)} by an approximate expression, and the measured screw rotation torque value. The ratio ρ ₁ with T is obtained. The maximum value ρ _1max is obtained and multiplied by F (R). That is, F (R) = ρ _1max a ₁ √R is an envelope that encompasses the maximum value of the data group of the table TA (Table 9). Further, the margin value A for safety is added and set as the allowable upper limit value T _{1 max} of the initial screw rotational torque.

  As described above, even if the number of data is small, the allowable upper limit value of the initial screw rotational torque obtained from the actual screw rotational torque value of injection molding is lower than the allowable upper limit value of the common fixed screw rotational torque. It is a value that is sufficiently effective for preventing breakage.

Further, in order to set a strict allowable upper limit value of the screw torque, the following measurement is performed. The number of moldings set in advance as the number of data to be aggregated is increased, and the screw rotation speed Tn at the screw rotation speed Rn is measured in the same manner as the setting of the allowable upper limit value of the initial screw rotation torque of the above-described five molding numbers.
First, the number of moldings set in advance as the number of data to be tabulated is increased, and the table TA (Table 9) is reset.
Screw rotation speed R (a, n) and screw rotation torque T (a, n) at each preset elapsed time from the start of measurement to the end of measurement, data DA {R (a, n), T (a, n )} In the table TA (Table 9). This continues measurement and storage of screw rotation torque at a screw rotation speed up to a preset number of moldings. Formula 16 which is an approximate expression representing the relationship between the screw rotation speed R (a, n) and the screw rotation torque T (a, n) is obtained from the data group stored in the preset table TA (Table 9). The method for obtaining the approximate expression and the method for setting the allowable upper limit value T _{2 max} of the screw rotational torque are as described above.
This continues measurement and storage of screw rotation torque at a screw rotation speed up to a preset number of moldings.

Here, the initial screw rotation torque allowable upper limit value is compared. If ρ _{1 max} a ₁ > ρ _{2 max} a ₂ , T _2max = ρ _2max a ₂ √R + A (Equation 18) is T _1max = ρ _1max a ₁ √R + A () at all screw rotation speeds. It becomes smaller than the mathematical formula 15). In this case, T _2max = ρ _2max a ₂ √R + A (Formula 18) that can keep the screw rotational torque low is set as the allowable upper limit value T _max of the screw rotational torque (see FIG. 11).

By substituting the screw rotation speed at each moment of measurement into Expression 15 that is an approximate expression that gives the allowable upper limit value T _max of the screw rotation torque or Expression 18 that is an approximate expression, the allowable upper limit value of the screw rotation torque at each moment When the screw rotation torque exceeding the allowable upper limit value is detected, the screw operation is changed or stopped so that the screw rotation torque is less than or equal to the allowable upper limit value.

  Alternatively, an allowable upper limit value of the screw rotation torque at the set value is obtained by substituting the set screw rotation speed for measurement into the approximate expression 15 or the approximate expression 18, and the screw exceeding the allowable upper limit value is obtained. When the rotational torque is detected, the screw operation is changed or stopped so that the screw rotational torque is less than or equal to the allowable upper limit value.

Next, when T _max is set, the molding number for setting the allowable upper limit value of the screw rotational torque is reset, and measurement is started again. Measurement and storage are continued in the table TA (Table 9) until the number of moldings set in advance is reached. When the preset number of moldings is reached, an approximate expression representing the relationship between the screw rotation speed R (a, n) and the screw rotation torque T (a, n) is obtained. From this point on, as long as the molding is continued, the allowable upper limit value of the screw rotational torque is updated repeatedly.

Seeking a of T = F (R) = a√R for all data measured until the preset number of molding cycles is, F the maximum value of a as _{a max (R) = a max} √R the table TA ( It is good also as an envelope which covers the maximum value of the data group of Table 9) (refer FIG. 11). Instead of adding the margin value A for safety, the safety factor B may be multiplied to obtain T _max = Bρ _max a√R (see FIG. 11).

FIG. 8 is a graph showing that the approximate expression representing the relationship between the screw rotational speed R _{k max} and the maximum screw rotational torque T _{k max} is a monotonically increasing linear function.
FIG. 9 is a graph showing that an approximate expression representing the relationship between the screw rotation speed R _{k max} and the maximum screw rotation torque T _{k max} is an n-order function (n> 1) of a quadratic function.
FIG. 10 is a graph showing that the approximate expression representing the relationship between the screw rotation speed R _{k max} and the maximum screw rotation torque T _{k max} is an irrational function such as a √function.
FIG. 11 is a graph showing the relationship between the screw rotation speed and the screw rotation torque and the allowable upper limit value of the screw rotation torque set by the approximate expression in the third embodiment of the present invention.
FIG. 12 is a flowchart of a processing algorithm for setting the allowable upper limit value of the screw rotation torque according to the third embodiment of the present invention.

Hereinafter, this flowchart will be described in accordance with each step.
Step C1: A fixed screw rotation torque allowable upper limit value is set.
Step C2: Reset the table TA (Table 9).
Step C3: Data obtained by measuring screw rotation speed R (a, n) and screw rotation torque T (a, n) at every preset elapsed time from the start of measurement to the end of measurement of the molding number a. DA {R (a, n), T (a, n)} is stored in the table TA (Table 5).
Step C4: The measurement is finished with a small number of moldings.
Step C5: Create an approximate expression F ₁ (R) from the data in the table TA (Table 9).
Step C6: The maximum ratio ρ _1max of the measured torque value and the approximate torque value is multiplied by F ₁ (R), and the torque value A for which safety is expected is added to F ₁ (R), and the screw rotation torque allowable upper limit value T _1max Set as.
Step C7: The table TA (Table 9) is reset. Resets the molding number for setting the screw torque upper limit.
Step C8: Screw rotational speed R (a, n) and screw rotational torque T (a, n) are measured at predetermined elapsed time from the start of measurement to the end of measurement for the molding number a, and data DA {R It is stored in the table TA (Table 9) as (a, n), T (a, n)}.
Step C9: Measurement is continued up to a preset number of moldings.
Step C10: The measurement is finished.
Step C11: Create an approximate expression F ₂ (R) from the table TA (Table 9).
Step C12: The maximum ratio ρ _2max of the actually measured torque value and the approximate torque value is multiplied by F ₂ (R), and the margin value A that allows for safety is added to F (R) to obtain T _2max .
Step C13: The table TA (Table 9) is reset.
Step C14: It is determined whether or not molding is completed. If molding is not completed, the process returns to Step C8. If molding is completed, the process ends.

In the first to third embodiments, the measurement up to the preset number of moldings may be the screw rotation speed and the screw rotation torque according to the preset screw moving distance.
In the above Embodiments 1 to 3, when screw rotation performs both forward rotation and reverse rotation during measurement, the screw rotation torque allowable upper limit value during screw reverse rotation is determined from the measurement of screw rotation torque during screw reverse rotation. May be set.

  In the above first to third embodiments, when molding is interrupted, the allowable upper limit value of the screw rotation torque so far is recorded in the mold file, and at the same time the allowable upper limit value of the screw rotation torque is read. May also be set so that the screw can be protected under the same conditions as immediately after the molding is interrupted. Further, when the mold file is read, it may be possible to select whether to continue updating the allowable upper limit value of the screw rotational torque or not.

  In the above first to third embodiments, when the resin is changed, or when conditions related to measurement (screw rotation speed, measurement back pressure, cylinder temperature, etc.) are changed, the screw rotation updated until just before the change. It is desirable to reset the allowable upper limit value of the torque and start over from the setting of the allowable upper limit value of the initial screw rotational torque under the condition that the screw operation is limited by the allowable upper limit value of the fixed screw rotational torque.

In the first to third embodiments, after the allowable upper limit value of the screw rotation torque is set, when the screw rotation torque exceeding the allowable upper limit value is detected, the screw operation is performed so that the screw rotation torque is equal to or lower than the allowable upper limit value. However, it is also possible to limit the drive torque of the rotary drive means for rotating the screw such as an electric motor to this allowable upper limit value.
FIG. 13 is a principal block diagram of an example of a control apparatus for an injection molding machine having a screw rotational torque monitoring function according to the present invention.
Reference numeral 1 denotes a processor that controls the entire injection molding machine, and is connected to a memory 2 including an input / output interface 3, servo interfaces 6 and 8, ROM, RAM, and nonvolatile RAM via a bus 5. . The memory 2 stores a program for realizing the above-described screw rotational torque monitoring function of the present invention. Servo motors M2 and M1 are connected to the servo interfaces 6 and 8, respectively. M1 is a screw rotation servomotor, and M2 is an injection servomotor.
The servo amplifier 9 is connected to a servo motor M1 and a pulse coder P1 as a speed detector. By detecting the rotational speed of the servo motor M1 by the pulse coder P1, the rotational speed of the screw of an injection molding machine (not shown) is detected. The servo amplifier 7 is connected to a servo motor M2 and a pulse coder P2 as a position / speed detector. By detecting the rotational position and rotational speed of the servo motor M2 by the pulse coder P2, the forward / reverse position and forward / reverse speed of the screw are detected.
The screw rotation torque can be obtained by measuring the magnitude of the drive current flowing through the servo motor M1 or incorporating a disturbance estimation observer in the servo amplifier 9. The processing of the disturbance estimation observer and the like is already well-known technology, and thus description thereof is omitted.
The input / output interface 3 is connected to a data input / output device 4 having a display means constituted by a liquid crystal display device, etc., and various commands and various parameters can be set by the input / output device 4. Can display various set values, screw rotation speed, screw position, screw rotation torque, and the like.

It is a flowchart which shows the algorithm of the process for setting the allowable upper limit of screw rotational torque (the 1). It is a flowchart which shows the algorithm of the process for setting the allowable upper limit of screw rotation torque (the 2). It is a graph which shows the relationship between the screw rotational speed and screw rotational torque in the 1st Embodiment of this invention, and the allowable upper limit of screw rotational torque. It is a graph showing that the approximate expression representing the relationship between screw rotation speeds R _{k max} and maximum screw rotating torques T _{k max} is a linear function of monotonically increasing. It is a graph showing that the approximate expression representing the relationship between screw rotation speeds R _{k max} and maximum screw rotating torques T _{k max} is an n-order function of the quadratic function (n> 1). Is a graph showing that the approximate expression representing the relationship between screw rotation speeds R _{k max} and maximum screw rotating torques T _{k max} is an irrational function such as √ function. It is a graph which shows the relationship between the screw rotation speed in the 2nd Embodiment of this invention, the screw rotation torque, and the allowable upper limit of the screw rotation torque set by an approximate expression. It is a flowchart of the algorithm of the process which performs the setting of the allowable upper limit of screw rotational torque which is the 2nd Embodiment of this invention (the 1). It is a flowchart of the algorithm of the process which sets the allowable upper limit of screw rotational torque which is the 2nd Embodiment of this invention (the 2). It is a graph showing that the approximate expression representing the relationship between screw rotation speeds R _{k max} and maximum screw rotating torques T _{k max} is a linear function of monotonically increasing. It is a graph showing that the approximate expression representing the relationship between screw rotation speeds R _{k max} and maximum screw rotating torques T _{k max} is an n-order function of the quadratic function (n> 1). Is a graph showing that the approximate expression representing the relationship between screw rotation speeds R _{k max} and maximum screw rotating torques T _{k max} is an irrational function such as √ function. It is a graph which shows the relationship between the screw rotational speed and screw rotational torque in the 3rd Embodiment of this invention, and the allowable upper limit of the screw rotational torque set by an approximation formula. It is a flowchart of the algorithm of the process which sets the allowable upper limit of screw rotational torque (the 1). It is a flowchart of the algorithm of the process which sets the allowable upper limit of screw rotational torque (the 2). It is a principal part block diagram of an example of the control apparatus of the injection molding machine provided with the screw rotational torque monitoring function of this invention.

Explanation of symbols

1 CPU
2 Memory 3 Input / output interface 4 Data input / output device with display means 5 Bus 6 Servo interface 7 Servo amplifier 8 Servo interface 9 Servo amplifier

Claims (9)

  Measuring means for measuring the screw rotation speed and screw rotation torque at predetermined time intervals or at predetermined screw movement distances during measurement, and storage means for storing the screw rotation speed and screw rotation torque obtained by the measurement means; The screw rotational speed and screw rotational torque stored in the storage means are input to a function assumed in advance, and a means for obtaining the maximum screw rotational torque at the screw rotational speed, and each screw rotation based on the obtained maximum screw rotational torque. A means for setting an allowable upper limit value of the screw rotation torque at the speed, and a means for changing or stopping the screw rotation operation when a screw rotation torque equal to or greater than the allowable upper limit value is detected during the subsequent measurement. Injection molding machine.   Measuring means for measuring the screw rotation speed and screw rotation torque at predetermined time intervals or at predetermined screw movement distances during measurement, and storage means for storing the screw rotation speed and screw rotation torque obtained by the measurement means; The screw rotational speed and screw rotational torque stored in the storage means are input to a function assumed in advance, and a means for obtaining the maximum screw rotational torque at the screw rotational speed, and each screw rotation based on the obtained maximum screw rotational torque. An injection molding machine comprising: means for setting an allowable upper limit value of screw rotational torque at speed; and means for limiting drive torque applied to the screw to the allowable upper limit value.   Measuring means for measuring screw rotation speed and screw rotation torque at predetermined time intervals or at predetermined screw movement distances during measurement, and measuring the screw rotation speed and screw rotation torque for a predetermined number of moldings by the measurement means. And storing the screw rotation speed and screw rotation torque obtained by measurement, and inputting the screw rotation speed and screw rotation torque stored in the storage means into a function assumed in advance. Means for obtaining an approximate expression representing the relationship between the speed and the maximum screw rotational torque at the screw rotational speed, means for setting an allowable upper limit value of the screw rotational torque by giving the screw rotational speed to the obtained approximate expression, and subsequent weighing When a screw rotation allowable torque exceeding the allowable upper limit value is detected during Injection molding machine, characterized by comprising means to change or stop the clew rotation.   Measuring means for measuring screw rotation speed and screw rotation torque at predetermined time intervals or at predetermined screw movement distances during measurement, and measuring the screw rotation speed and screw rotation torque for a predetermined number of moldings by the measurement means. And storing the screw rotation speed and screw rotation torque obtained by measurement, and inputting the screw rotation speed and screw rotation torque stored in the storage means into a function assumed in advance. Means for obtaining an approximate expression representing the relationship between the speed and the maximum screw rotational torque at the screw rotational speed, means for setting an allowable upper limit value of the screw rotational torque by giving the screw rotational speed to the obtained approximate expression, and applying to the screw A means for limiting the driving torque to the allowable upper limit value is provided. Injection molding machine, wherein the door.   Means for updating the upper limit value of the screw rotation torque based on the screw rotation speed and the screw rotation torque measured at predetermined time intervals or every predetermined distance after the allowable upper limit value of the screw rotation torque is set; The injection molding machine according to any one of claims 1 to 4, wherein the injection molding machine is provided.   The injection molding machine according to any one of claims 1 to 4, wherein the upper limit value of the screw rotation torque is set for each of a case where the screw rotates forward and a case where the screw rotates reversely.   The injection molding machine according to any one of claims 1 to 4, further comprising means for storing the set allowable upper limit value of the screw rotation torque in association with mold information.   The injection molding machine according to any one of claims 1 to 4, wherein a plurality of functions are prepared as the function assumed in advance, and a means for selecting any one of the functions is provided.   The injection molding according to claim 3 or 4, wherein the allowable upper limit value of the screw rotation torque is set by adding a constant torque to the screw rotation torque maximum value or multiplying by a constant coefficient. Machine.

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